105 research outputs found
Spatio-Temporal Scaling of Solar Surface Flows
The Sun provides an excellent natural laboratory for nonlinear phenomena. We
use motions of magnetic bright points on the solar surface, at the smallest
scales yet observed, to study the small scale dynamics of the photospheric
plasma. The paths of the bright points are analyzed within a continuous time
random walk framework. Their spatial and temporal scaling suggest that the
observed motions are the walks of imperfectly correlated tracers on a turbulent
fluid flow in the lanes between granular convection cells.Comment: Now Accepted by Physical Review Letter
Striation and convection in penumbral filaments
Observations with the 1-m Swedish Solar Telescope of the flows seen in
penumbral filaments are presented. Time sequences of bright filaments show
overturning motions strikingly similar to those seen along the walls of small
isolated structures in the active regions. The filaments show outward
propagating striations with inclination angles suggesting that they are aligned
with the local magnetic field. We interpret it as the equivalent of the
striations seen in the walls of small isolated magnetic structures. Their
origin is then a corrugation of the boundary between an overturning convective
flow inside the filament and the magnetic field wrapping around it. The outward
propagation is a combination of a pattern motion due to the downflow observed
along the sides of bright filaments, and the Evershed flow. The observed short
wavelength of the striation argues against the existence of a dynamically
significant horizontal field inside the bright filaments. Its intensity
contrast is explained by the same physical effect that causes the dark cores of
filaments, light bridges and `canals'. In this way striation represents an
important clue to the physics of penumbral structure and its relation with
other magnetic structures on the solar surface. We put this in perspective with
results from the recent 3-D radiative hydrodynamic simulations.Comment: Accepted for publication in A&
Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows
The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research
Limb Spicules from the Ground and from Space
We amassed statistics for quiet-sun chromosphere spicules at the limb using
ground-based observations from the Swedish 1-m Solar Telescope on La Palma and
simultaneously from NASA's Transition Region and Coronal Explorer (TRACE)
spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond
resolution obtained after maximizing the ground-based resolution with the
Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained
specific statistics for sizes and motions of over two dozen individual
spicules, based on movies compiled at 50-second cadence for the series of five
wavelengths observed in a very narrow band at H-alpha, on-band and in the red
and blue wings at 0.035 nm and 0.070 nm (10 s at each wavelength) using the
SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from
TRACE. The MOMFBD restoration also automatically aligned the images,
facilitating the making of Dopplergrams at each off-band pair. We studied 40
H-alpha spicules, and 14 EUV spicules that overlapped H-alpha spicules; we
found that their dynamical and morphological properties fit into the framework
of several previous studies. From a preliminary comparison with spicule
theories, our observations are consistent with a reconnection mechanism for
spicule generation, and with UV spicules being a sheath region surrounding the
H-alpha spicules
Ionic liquids at electrified interfaces
Until recently, âroom-temperatureâ (<100â150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)â(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of âfirst-generationâ room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the âlater generationâ RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in âcocktailsâ of oneâs choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost âuniversalâ solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) âsister-systemsâ.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules
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The European Solar Telescope
The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French TĂ©lescope HĂ©liographique pour l'Ătude du MagnĂ©tisme et des InstabilitĂ©s Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems
Efficient discovery of anti-inflammatory small-molecule combinations using evolutionary computing
The control of biochemical fluxes is distributed, and to perturb complex intracellular networks effectively it is often necessary to modulate several steps simultaneously. However, the number of possible permutations leads to a combinatorial explosion in the number of experiments that would have to be performed in a complete analysis. We used a multiobjective evolutionary algorithm to optimize reagent combinations from a dynamic chemical library of 33 compounds with established or predicted targets in the regulatory network controlling IL-1ÎČ expression. The evolutionary algorithm converged on excellent solutions within 11 generations, during which we studied just 550 combinations out of the potential search space of ~9 billion. The top five reagents with the greatest contribution to combinatorial effects throughout the evolutionary algorithm were then optimized pairwise. A p38 MAPK inhibitor together with either an inhibitor of IÎșB kinase or a chelator of poorly liganded iron yielded synergistic inhibition of macrophage IL-1ÎČ expression. Evolutionary searches provide a powerful and general approach to the discovery of new combinations of pharmacological agents with therapeutic indices potentially greater than those of single drugs
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